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Arabian Sea, Red Sea, Persian Gulf

This SeaWiFS image shows a massive dust storm in Iran and Pakistan blowing out into the Arabian Sea.

Arabian Sea


The northern part of the Arabian Sea gently slopes over the Indus cone towards the deep sea. Broad shelves lie along the western coast of India, and narrow, steep continental shelf breaks along most other coasts. The submarine Carlsberg ridge represents the southern boundary of the Arabian Sea. In former times, the sea has long been an important trade route between India and the West.


The monsoons of the Arabian Sea are remarkably strong and steady. Typical coastal ecosystems are mangroves e.g. along the coast of Iran. At low tide, the shore zone is a sea of waving white claws of the fiddler crabs. Thirty fish species can be found hidden in the creeks and mangrove forests along the coast, with approximately 85 per cent of these migrating from the sea, while the remainders are known as mangrove and estuarine residents.


Most fish found here are juveniles since the mangroves are perfect nursery grounds. At least 25 of the regional species are considered commercial or food fishes. Additionally, over half a dozen species of tasty shrimps and crabs live in the mangroves representing an important stock for local fisheries.



The Red Sea is a long extended, narrow and fully enclosed continental sea. (Photo: NASA, SeaWiFS)

Red Sea


Both the Red Sea and the Persian Gulf are long extended, narrow and fully enclosed continental seas. While the Red Sea is deep and shows a lively bottom topography due to seafloor spreading, the Persian Gulf floor is extremely flat and shallow throughout. The deep Arabian Sea is the northwestern part of the Indian Ocean lying between Arabia and India.


The Sinai Peninsula divides the northern part of the Red Sea into the shallow Gulf of Suez to the west and the deep Gulf of Aqaba to the east. To the south, the Red Sea is connected via the Gulf of Aden to the Arabian Sea.


Due to the dry, hot climate and the surrounding desert landscapes, the Red Sea has little freshwater supply resulting in high salinity. Nevertheless, the sea has a rich variety of fish life and corals.


The Red Sea was an important trade route in history. Its importance declined with the discovery of the sea route around Africa in the late 15th century. The opening of the Suez Canal in 1869 made the Red Sea one of the major shipping routes connecting Europe with East Asia and Australia. The sea is dotted with dangerous coral reefs and submerged islands, which have caused many ship losses.



Der Persische Golf erstreckt sich vom Schatt el Arab-Delta im Norden (links oben) bis zur Straße von Hormus (Bildmitte), die im Süden den Golf mit dem Arabischen Meer verbindet. (Photo: NASA, SeaWiFS)

Persian Gulf


The Persian Gulf extends from the Shatt al Arab delta to the Strait of Hormuz, which links it over the Gulf of Oman with the Arabian Sea.


Besides oil, the Persian Gulf region also has huge natural gas reserves. The region holds 65 per cent of the World's oil reserves and 34 per cent of the total proven World gas occurrences. In 2000, the Persian Gulf countries like Bahrain, Iran, Iraq, Kuwait, Qatar, Saudi Arabia, and the United Arab Emirates produced nearly 28 per cent of the World's oil. Serious incidents affected the environment of the gulf in the past decades. While oil spills from the heavy traffic of tankers were serious enough since, oil spills from the 1983 Iran-Iraq War and during the Gulf War in 1991 have been catastrophic.



A New Ocean Develops


The Red Sea represents - in geological time scales - a young ocean just evolved from the state of continental rifting towards seafloor spreading. However, first we should put a brief glance on the geological expressions called ”rifting” and ”seafloor spreading” used in the previous sentence.


Rifting is the beginning process of slow opening of a new ocean basin from a continental tectonic graben system (rift valley) towards the submarine volcanic formation of new oceanic crust, called seafloor spreading. The divergent plate tectonic boundary creates a new ocean basin that begins so narrow that it barely exists, like the Red Sea today, and spreads to thousands of kilometers width over millions and millions of years, like the modern Atlantic or Pacific Oceans. Rifting events mostly begin within continental boundaries, and tear large continents into smaller pieces, each a separate continent then, like can be observed in the modern eastern Africa.


Let us now take a closer look to the Red Sea. Driven by up rising hot magma plumes from the deeper earth, the Arabian continental plate and the African plate started to drift apart some 55 million years ago. A tectonic graben and fault system developed and roughly 25 million years ago the first phase of the Red Sea formation began. The break-up of the Arabian plate from Africa started - accompanied by intense magmatic activity - and water intruded into the newly evolving narrow ocean from northern directions. Seafloor spreading in the developing ocean started roughly 15 to 20 million years ago. Today, it is generally accepted that in the past 5 million years seafloor spreading formed a mid-oceanic ridge at least in the southern Red Sea and in the Gulf of Aqaba. Based on the good match of the African and Arabian coastlines on both sides of the Red Sea, other scientists hypothesize that seafloor spreading formed new oceanic basement in the entire Red Sea during that period. Evidently, the modern Red Sea floor spreads with a velocity of roughly 15 to 20 millimeters per year.



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